Frequency changing radio receiving apparatus



Aug. 18, 1936. Y. ROCARD 7 2,051,104

FREQUENCY CHANGING RADIO RECEIVING APPARATUS Filed Jan. 15, 1932 YVESROCARD INVENTOR mmw;

ATTORNEYS Patented Aug. 18, 1936 mes- FREQUENCY CHANGING RADIO RECEIVINGAPPARATUS Yves Rocard, Paris, France, assignor to La Radiotechnique,Paris, France, a corporation.

of France 6 Claims. (01. 250-20) 7 This invention relates to frequencychanging radio receiving apparatus and makes possiblethe regulations ofthe circuit tuned. to the frequency received and of the heterodynecircuit in. such a 5 frequency changing system, for. example, in avsuperheterodyne radio telephonic receiver, en-' tirely. independent ofone another. -The invention has for its principal object the eliminationof the amplification blanks which these receivers 10 always present onthe scale of the frequencies to be received, and enables, in a simpleand practical manner, the single control of the tunings of, the circuitsto be eifected.

Various illustrative examples of carrying the invention into effect aregiven below, but they are to'be understood as being non-limitative, theinvention being more particularly set forth in the appended claims.

The invention will now be described withref- 50 erence to the annexeddrawing, in which:-

Figure 1 represents the diagram of a superheterodyne circuit withdual-grid frequency changer, arranged according to the invention.

Figure 2 represents diagrammatically a special thermionic tubeconstructed in accordance with the invention. a a 1 In the drawing,identical references indicate the same parts. 7 Two examples of theundesirable phenomena which are produced. when the independence oftuning of the circuits obtained'in accordance with this invention isabsent, will be described; actually this independent of tuning is notattained in any previously known systems.

5 Considering the radio modulator represented in Figure 1, there isshowna dual-grid thermionic tube l for effecting frequency changefollowed by a mean frequency filter M. The input circuit of the controlgrid 2'of the tube consists'generally f of a frame aerial 4 tuned by avariable condenser 5. This-antiresonant circuit is thus shunted by thecapacities formed between the control grid 2 and oscillating grid 3 andbetween the control grid 2 and the plate 6 of the dual-grid tube, each 5followed by the impedance which charges the corresponding electrode; itwill be understood that if this grid-to-grid or grid-to-plate capacitycomes into resonance-series with the charging impedance in question(which will be for example the oscillating circuit l-3 of theheterodyne), the input circuit formed by the tuned frame aerial will beshunted by a resulting zero impedance: At the frequency for which thiseffect is produced the frame aerial circuit will, therefore, give nosignal to the grid 2, and the receiving. station will possess a."blankspot in its tuning range. If the beat is changed by manipulating theheterodyne condenser 8, this effect may be avoided, but in such case aneifect quite as undesirable is produced, namely the 5 tuned frame aerialis placed in resonance-series by: the capacity formed between the grid 2and the other electrodes short-circuiting the oscillating circuit of theheterodyne.

Now, with the capacities actually formed be- 10 tween the electrodes ofdual-grid tubes and with the order of the mean frequencies employed,these phenomena are actually produced in the range of broadcastfrequencies, and they are only avoided by using thesecond or thirdharmonics 5 of they heterodynea process which cannot be generallyemployed over the whole scale without inconvenience, for the fundamentalof the heterodyne will sometimes be very close to the meanfrequency, andfurthermore, the amplitude of the harmonics in question. variesconsiderably over the scale of frequencies.

In addition to the serious disadvantages described above, theinterdependence or mutual reactionof thecircuits always introduces amutual dependence between the regulations of the two circuits ll'5 and,'l-8 which renders the employment of a single control practicallyimpossible, owing to the dependence being subject to sudden variation onthelscale of the frequencies and .of variation from one tube to another.

. The present invention enables the regulations of the circuits tuned tothe Wave frequency to be received independent of the regulation of theheterodyne, and vice versa. By this is meant that the position of thevariable member (for example, the condenser 5) which enablesthe'receiving aerial circuit to be tuned to a carrier wave,is.independentof any frequency value which is given to the. heterodyne'l8; It..is' establishedv that thertuningsto thecarrier wave. and theheterodyne follow simple and regular laws as a function, for example, ofthe variable capacities, which will permit a single control to beemployed, and in any case eliminate the blank spots above referred to.

In the case of a radio modulator, a tube (for example, a dual-grid ortri-grid) is employed in which a control electrode modulates anoscillation created by the same tube. In Figure 1, such a tube isindicated at I. In this case, the invention provides that this controlelectrode is surrounded by a screen l3 arranged to be subjected to afixed potential by means of a battery ID which will appreciably cancelthe capacity of the grid 2 with respect to all the other electrodes,

' 1 trodeand the plate of an embodiment constructed in accordance withthe invention, of a tube. The pinch of the tube is indicated at l1, thecathode at [5 (assumed on the drawing to be indirectly heated), theoscillating grid at 3, the screen at I; serving completely to insulatethe control grid 2 asabove described, and the plate or anode at 6. Theconnection of the control grid with the external circuits will beeffected by aiconductor [6, the

passage of which through the bulb will be removed from the zone of theconnections for the other electrodes extending through the pinch ll ofthe tube, and arranged for example at the top of the tube bulb.

'What I claim is: V

1. In a frequency changing radio receiver, the combination of a tubehaving a plurality of electrodes including among others a cathode andconditioned to be traversed by an electronic flow issuing from thecathode, an oscillating circuit connected to one of said electrodes,coupling means in the circuit of another of said electrodes for couplingsaid last circuit together with said oscillating circuit so as to causea predetermined radio frequency current to be locally generated in saidoscillating circuit, a source of a different radio frequency connectedto still another of said electrodes, capable of controlling theelectronic flow, and means for suppressing the capacity between saidelectrode which is connected to said,

oscillating circuit and said last controlling elecsaid tube.

.2. In a frequency changing radio receiver, the combination of a tubehaving a plurality of electrodes including among the same a cathode andconditioned to be traversed byan electronic flow issuing from thecathode, an oscillating circuit connected to one of said electrodes,coupling means in thecircuitof another of said electrodes for couplingsaid last circuit together with said oscillating circuit so as to causea predetermined radio frequency current to be locallygenerated in saidoscillating circuit, a source of a different radio frequency connectedto still another of said electrodes, capableof controlling theelectronic flow, and .a screen interposed between said electrode whichis connected to said oscillating circuit and said last controllingelectrode and the plate of said tube.

3. In a frequency changing radio receiver, the combination of a tubehaving a plurality of electrodes including among the same a cathode andconditioned to be traversed by an electronic flow issuing from saidcathode, an oscillating circuit connected to one of said electrodes,coupling means in the circuit of another of said electrodes for couplingsaid last circuit together with said oscillating circuit so as to causea predetermined radio frequency current to be locally generated in saidoscillating circuit, a source of a different radio frequency connectedto still another of said electrodes, capable of controlling theelectronic flow, a screen interposed between said electrode which isconnected to said oscillating circuit and said last controllingelectrode and the plate of said tube, and means for subjecting thescreen to a predetermined potential.

4. In a frequency changing radio receiver, the combination of a tubehaving a plurality of electrodes including among the same a cathode andconditioned to be traversed by an electronic flow issuingfrom saidcathode, at least one of the other electrodes being adjacent to thecathode, an oscillating circuit connected to said electrode which 7 isadjacent to said cathode, coupling means in the. circuit of a third ofsaid electrodes,

for couplingsai'd last circuit together with said oscillating circuit soas to cause a predetermined radio frequencycurrent to be locallygenerated. in said oscillating circuit, a source of a different radiofrequency connected to still another of said electrodes, capable ofcontrolling the electronic flow and extending between the plate andsaidelectrode which is adjacent to said cathode, and a screenextendingbetween said lastcontrolling electrode and the local radio frequencyelectrode adjacent to the cathode.

v5. In a frequency changing radio receiver, the combination of a tubehaving a plurality of electrodesincluding among the same a cathode andconditioned to be traversed by an electronic flow issuing fromsaidcathode, an oscillating circuit connected to another of said electrodes,coupling means in the circuit of a third of said electrodes for couplingsaid last circuit together with said oscillating circuit soras to causea predetermined radio frequency current to be locally generated in saidoscillating circuit, a source'of a different radio frequency connectedto still another of said electrodes, capable of controlling'theelectronic flow, there being a plate, and a screen extending betweensaid last controlling electrode and thethird or local radio frequencyelectrode and also between said controlling electrode and the plate.

7 6. An electronic tube according to the combination in claim 1, whereinthe controlling electrode passes through the top of the envelope orbulb, while the other electrodes including at least the cathode, plate,local radio frequency electrode and screening electrode are connected toleads extending through the pinch of the tube.

YVES 'ROCARD.

